1. Technical Field
The present invention relates to actuators and, in particular, to actuators that are driven by flow movement of fluid.
2. Related Art
Pneumatic actuators that are driven by moving air caused by a pressure applied to the air are available as power sources for robots or the like. A typical pneumatic actuator has a syringe-like structure composed of a cylinder and a piston, and may be equipped with a tank and a compressor for pumping compressed air to the cylinder. As the compressed air is pumped out from the compressor to the cylinder through the tank, the piston that is a moveable part operates. An actuator having such a structure is described in, for example, JP-A-2005-230949 (Patent Document 1).
However, the actuator having the structure described above needs a tank and a compressor, which would result in a large-scale structure. In this respect, JP-A-2001-248601 (Patent Document 2) describes an actuator that uses shape memory alloy, wherein a piston connected to the shape memory alloy is slidably moved by heating and contracting the shape memory alloy.
The actuator described in Patent Document 2 can be structured in a smaller size, compared to the structure described in Patent Document 1, but needs to use parts composed of relatively expensive material such as shape memory alloy. Further, as the actuator needs to be heated, there is an issue concerning energy efficiency. Moreover, when the piston that is a moveable part is moved by using shape memory alloy, its movements become relatively rigid, compared to other related technologies that drive a moveable part by flowing movement of fluid.